1. Field of the Art
The present invention relates to a timer for controlling the operation of an electrical apparatus.
2. Description of the Related Art
A timer is conventionally used to start and/or end an operation of an electrical apparatus such as an air conditioner, TV set or VCR, when the timer reaches an operation time, which can be either an operation start time or operation end time.
There are known two types of such timers (hereafter referred to as a first type and a second type) for setting an operation time of the apparatus. One type of timer (first type) is disclosed in U.S. Pat. No. 4,843,384, which designates the operation time by inputting a target time (clock time, for example 18:00). The timer, which includes a clock, controls the apparatus when a current time of the clock reaches the target time.
In the other type of timer (second type), the operation time is designated by inputting a time interval, for example 5 hours, between the target time at which the operation of the apparatus is started or ended and an actual time when the timer is set. The second timer controls the apparatus at the end of the time interval.
The first type of timer operates on the basis of the current time of the clock. Therefore, it does not work without setting the clock. Usually, setting the clock is done by designating an initial time. The first type of timer is generally contained in a remote controller which is energized by electric power from a battery. When the power supplied from the battery fails, the clock in the timer stops counting time and the current time data of the clock is cleared. As a result, it is required to reset the clock every time the battery is replaced.
The second type of timer does not require setting the clock. However, it is troublesome for a user who is accustomed to using the first type of timer, since for the second type, it is necessary to calculate the time interval between the target time and an actual time.
There is known a modified timer having a combined function of both types of timer wherein the operation start time is designated by inputting the target time and the operation end time is designated by inputting the desired time interval. However, in the modified timer, it is required to set the clock before setting the operation start time.